1. Field of the Invention
In general, embodiments of the present invention relates to a property measurement apparatus for measuring a stress which is generated in a sample when a distortion is given to the sample and measuring the impedance of the sample and relates to a property measurement method to be adopted by the property measurement apparatus. More particularly, the embodiments of the present invention relates to a technology for measuring both the dynamic viscoelasticity and dielectric characteristic of a sample at the same time in one measurement.
2. Description of the Related Art
In the past, a rotary rheometer has been used widely for measuring dynamic viscoelasticity. In general, a rotary rheometer has a configuration in which a sample is sandwiched by a planar lower plate fixed on the rheometer apparatus and a conical or planar upper plate having an upper surface linked to a bearing by a shaft. In such a configuration, the upper plate is rotated or vibrated in order to give a distortion to the sample and a stress caused by the distortion is then measured.
At that time, the frequency of the rotation or the vibration applied to the sample can be changed in order to obtain dynamic information. Then, the viscoelasticity of the sample is found on the basis of the dynamic information. In the rheometer having such a configuration, an air bearing can be used as the bearing in order to allow an infinitesimal stress to be detected and allow a sample having a low degree of viscosity to be measured effectively.
In place of the configuration in which a sample is sandwiched by the lower and upper plates as described above, the rotary rheometer may have a configuration in which an outer cylinder and an inner cylinder or an inner cylindrical column are provided concentrically, and a sample is injected into a gap between the outer cylinder and the inner cylinder or the inner cylindrical column, being subjected to measurements. In the case of the rheometer having such a configuration, the inner cylinder (or the inner cylindrical column) or the outer cylinder is rotated or vibrated and a stress caused by the rotation or the vibration is detected.
In the rheometer having the configuration including a pair of lower and upper plates as described above, the configuration of sandwiching a sample between the plates is regarded as a capacitor. Thus, by applying a voltage between the plates, the dielectric response of the sample can be observed. In this case, however, physical contact of a conductor with the upper plate is required in a form as electrical contact. As described above, the upper plate needs to be rotated or vibrated in order to measure the dynamic viscoelasticity of the sample. To put it concretely, when measuring both the dynamic viscoelasticity and dielectric characteristic of a sample by making use of the existing property measurement apparatus, at least, two surfaces coming into contact with the sample are manufactured from a conductor material and, in addition, a metallic clip or the like is brought into contact with the rotation shaft in order to establish electrical contact with the two surfaces.
In addition, in the past, there has also been proposed a method for finding the viscosity coefficient and dielectric constant of liquid part of a subject of measurement from values obtained as a result of measurements of propagation-speed and propagation-loss differences between elastic surface waves which are input when comb-shaped electrodes forming elastic surface propagation lines are submerged into the liquid part of the subject of measurement. For more information on the proposed method, the reader is suggested to refer to Japanese Patent Laid-Open No. Hei 6-109710 (hereinafter referred to as Patent Document 1) and Japanese Patent Laid-Open No. Hei 6-194346 (hereinafter referred to as Patent Document 2).